128 FLORIDA GEOLOGICAL SURVEY-THIRD ANNUAL REP)R7.
tide. The oyster reef extends about two hundred feet along the face of the bluff.
The unusual thickness of the loose yellow sands at the top of the bluff is due to the fact that the upward moving currents of air carry sand as it is loosened along the face of the bluff to the top where it accumulates as a sand dune.
Rose's Bluff also on the Florida side of the river about two miles below Crandall is semi-circular in shape and is fully two miles long. The following section was made near the middle of this bluff:
Dark colored sand and soil .................................. 4 feet
Dark iron-stained sand (hardpan) ............................. 7 feet
Ochre yellow sand .......................................... 8 feet
Sand with some clay ....................... ................ 5 feet
Sandy shell bearing marl, blue, oxidizing yellow ..............4 feet
Sloping to waters edge at low tide.......................5 feet
33 feet
AREA OF ARTESIAN FLOW IN NASSAU COUNTY.
The part of Nassau County in which flowing wells can be obtained is indicated on the accompanying map by shading. Flowing wells may be obtained as shown by the map, (p. 135) in approximately the eastern two thirds of the county. A relatively small area, including the ridge already mentioned lying near the western part of the county and extending north and south parallel with the St. Marys River stands too high to obtain flowing wells. In this section, however, non-flowing artesian water may be obtained which will stand within a few feet of the surface.
LOCAL DETAILS
CALLAHAN.
There are several flowing wells at and in the vicinity of Callahan, varying from 410 to 489.7 feet in depth. Three different water-bearing strata are reported in all the deeper wells at Callahan, the first occurring at about 5o, the second at from i6o to 200, and the third at 400 to 425 feet. The water from the first stratum does not flow but rises to within 6 to 10o feet of the surface, and is found in a shell formation. The water from the other two strata rises from 28 to 48 feet above the surface.
The first deep or artesian well at Callahan was drilled in 1904. This well was put down at the instance of several of the residents,